The typical determination of reliability of a system is straightforward yet potentially very time-intensive. To assess the reliability of a system one needs only to identify the total different possible states of the system (with respect to the operational status of each component), determine which of these states result in the failure of the specific system, calculate the probabilities of each of these failure states occurring, and sum them to arrive at the overall reliability.
In the case of an electrical power system, a failure of the system is generally considered to be loss of power to a particular load, e.g., a starting motor, a load bus, etc. The task of assessing the reliability of an electrical power system is formidable because there are ordinarily several components to the system, and with each component having at least two possible states, operational or non-operational there are at least 2 raised to the power of the number of total system components possible states. In even a modest electrical power system the number of components could be 20 or more, which establish a total number of possible states in excess of 1 million.
More than simply assessing the reliability of a single system, system designers and engineers typically wish to evaluate several system designs. Having to assess millions of possible operational states for each system design is time and cost prohibitive.
Computer added engineering tools have been available for a number of different applications. For example U.S. Pat. No. 4,847,795 discusses a system for diagnosing defects in electronic assemblies. Actual test data is gathered and analyzed to determine failure patterns, which are used to estimate failure probabilities given certain constraint conditions.
In U.S. Pat. No. 5,138,694 a qualitative reasoning approach is applied to observed failure symptoms to identify the reasons for a particular failure. The system does not contemplate predicting failures, and instead focuses on determining failure causes and employs a fault tree analysis approach.
The disclosure of U.S. Pat. No. 5,144,563 is directed to a system to aid in the design of computer chips, and more particularly, to reducing wiring lengths between components. Similarly, U.S. Pat. No. 5,257,201 discloses a system that attempts to reduce the number of connections in an integrated circuit. And, Japanese patent no. 59-184969 discloses use of the "minimum cut" method to optimize integrated circuit design, again by reducing wiring lengths.
In U.S. Pat. No. 5,293,585 an expert system is disclosed apart from any particular application. The expert system implements a rule-based reasoning approach to failure analysis and fault detection.
U.S. Pat. No. 5,386,498 also describes an expert system capable of drawing conclusions based on experience. Knowledge bases are built and updated through a proposed process.
An article appearing in the July, 1986 issue of Computer magazine discusses a system for troubleshooting failed electronics using artificial intelligence. The system uses a fault detection and isolation approach to identify a failed hardware device within a larger system.
It is clear numerous computer based systems and methods are available to assist in the design of electrical systems and components. However, there remains a need for a tool for quickly evaluating the reliability of system designs, and particularly power distribution system designs and variations and alternatives thereto.